Make sure the block is dry, then rub a little grey silicon (other kinds of sealer are just as good, this is what I use) around with your finger. Not too much. then drive the plug in so the edge is flush with the block. Do not push it in so far that it contacts the cam. That would be bad.
God Bless.
Tim http://yblockguy.com/
350ci Y-Block FED "Elwood", 301ci Y-Block Unibody LSR "Jake", 312ci Y-Block '58 F-100, 338ci Y-Block powered Model A Tudor
tim@yblockguy.com Visalia, California Just west of the Sequoias